1. Field of the Invention
The present invention relates to a document paper size detection apparatus and method in a facsimile. Specifically, this invention is a document paper size detection method, wherein a charge coupled device (CCD) module performs two shifting motions for detecting the size of document paper and for reading the document when a document is fed in in a paper feeding unit, and, by using the paper size detected, only valid image signals will be obtained, and the image will be modulated based upon an accurate reduction or enlargement ratio when copied or transmitted.
2. Discussion of Related Art
A typical facsimile, as shown in FIG. 1, consists of a central processing unit (CPU) 10 for controlling overall operation of the facsimile according to a document processing program, a memory 20 for storing a password, a present time, received data, etc., an operating panel equipment (OPE) 30 having a key input unit with many keys, such as a received document output key and numeral keys, for generating signals corresponding to key input, and a display unit for displaying the operation state of the facsimile according to the display data of CPU 10, a scanner 40 for scanning a documenta and converting the image of the document into binary data and sending the data to CPU 10, a MODEM 50 for modulating or demodulating signals which are input to or output from CPU 10, a network control unit (NCU) 60 for communicating with MODEM 50 under the control of CPU 10, a printer 70 for printing the received document, the copied document or other data on paper under the control of CPU 10, a sensor 80 for checking whether there a document to be scanned or sheets of paper to be printed on and sending the result of the check to CPU 10, and speaker 90 for converting voice data into voice signals under the control of CPU 10.
Such conventional facsimiles have different specifications and use various apparatuses and methods for detecting the size of document paper. FIG. 2 shows an example one such apparatus for detecting paper of different sizes, such as A3, B4, Letter and A4. Accordingly, there are four classes grouping document paper according to size in a typical facsimile. If a user moves a right guide 2a6 or left guide 2a8 side to side, the two guides move simultaneously outward or inward the same distance because guide gear 2a10 is engaged with both guides. A pair of sensors 2a2 and 2a4 are engaged with right guide 2a6 for outputting a pair of sensor signals, such as binary values. For example, if the sensors output binary values 00 a detection of paper size A4 is made. Similarly an output of 10 corresponds to a detection of paper size LTR, an output of 01 corresponds to a detection of paper size B4, and an output of 11 corresponds to a detection of paper size A3.
The paper width in a reception unit is usually set to 216 mm(Ltr) or 210 mm (A4), and four classes grouping reduction ratios are employed in a facsimile. Values, which corresponds to the widths of sheets of document paper and is detected by the sensor, are as follows:
TABLE 1 ______________________________________ Width of paper Reading ratio Sensor 2a2 Sensor 2a4 ______________________________________ A4 .gtoreq. width 100% Off Off A4 .ltoreq. width &lt; B4 about 85% On Off B4 .ltoreq. width &lt; A3 about 73% Off On A3 .ltoreq. width about 70% On On ______________________________________
The user must adjust the reduction ratio based upon the ratio of the width of document paper to recording paper by setting guides 2a6 and 2a8. If the width of document paper is wider than the recording paper or if guides 2a6 and 2a8 are adjusted incorrectly indicating a document wider in width than the recording paper, there is a problem that a reduction fitting output data to the recording paper is not properly performed, or data is reduced too much to be read.
FIG. 3A and 3B are respectively a sectional view and a plan view of a conventional scanner. As shown in FIG. 3A, the size of document paper is detected without a special sensor. Once a user adjusts a guide 3a6 to a document, a contact image sensor (CIC) 3a18, which is a reading sensor, reads optical sensor reflecting unit 3a16 to detect the size of document paper, before the document reaches a reading location by drive roller 3a12 , thus obtaining only valid data, when reading the document, by abandoning portions other than the document paper. Roller 3a14 is a discharge roller for discharging the scanned document from the scanner. If the document paper is slanted because of a mistake in adjusting guide, 2a6, or if the document does not reach the reading location until after the reading operation starts, rib 3a20 or hole 3a22 (FIG. 3B) in the reading unit is read, resulting in a black line on a recording paper. That is, when a portion where the document is not placed is read, light is not reflected, so black is read. Consequently, the edge, leading portion, or rear portion of the recording paper becomes black when printing is completed. When using a white roller, which keeps a regular reading distance and moves the document paper at a regular speed, optical sensor reflecting unit 3a16 cannot discriminate the white paper from the white roller, so the conventional method may not be correctly utilized to detect the size of document paper.
As illustrated, when scanning a document, it is possible to incorrectly adjust the paper guides and thus an error occurs in the reduction ratio according to the ratio of a document paper width to a recording paper size in the conventional method.